This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Breast milk transmission of HIV is a leading cause of infant HIV/AIDS in the developing world. Remarkably, only a small minority of breastfeeding infants born to HIV-infected mothers contract HIV via breast milk exposure, raising the possibility that immune factors in the breast milk confer protection to the infants who remain uninfected. We wanted to model the HIV viral evolution, cellular tropism and immune responses in breast milk of HIV-infected mothers by studying breast milk in the SIV-infected rhesus macaque model. Since it is however not feasible to use breeder female rhesus monkeys in these studies, we optimized a protocol to pharmacologically induce lactation through hormone manipulation.